Reciprocating carriage drive



Aug. 21, 1951 Filed July l5, 1946 J. M. CHRISTMAN 2,565,020

RECIPROCATING CARRIAGE DRIVE:

5 Sheets-Sheet l UWE/WOR.

1 Aug. 21, 1951 J. M. HRISTMAN 2,565,020

RECIPROCATING CARRIAGE DRIVE Filed July 13, 1946 5 sheets-sheet 2 INVENTOR. 752,1 ff/2me fwd.

Aug. 2l, 1951 .L M. CHRISTMAN RECIPROCATING CARRIAGE DRIVE 5 Sheets-Sheet 5 Filed July 13, 1946 Aug* 21, 19517 .1. M, CHRISTMAN 2,565,020

RECIPROCATING CARRIGE DRIVE Filed July 13, 1946 5 Sheets-Sheet 4 vfm.

, /7 Tra/rfv Erf.

Aug. 2l, 1951 5 Sheets-Sheet 5 Filed July 13, 1946 Patented Aug. 21, 1951 UNITED STATES PATENT OFFICE RECIPROCATING CARRIAGE DRIVE Application July 13, 1946, Serial No. 683,454

2 Claims.

This invention relates to grinding machines, and particularly to a grinding. machine of novel and improved construction employing a continuously driven double lead feed screw and mechanism by which the lead screw reciprocates a work head.

The machine of the present invention employs the usual reciprocable table, slidably mounted upon a suitable base, carrying a work head having means to rotatably support a piece of work. It is desirable in a machine of this nature that movement of the table in each direction be at a uniform rate of speed and that reversal from one direction of travel to the other occur with no appreciable loss of time. Further, the length of the stroke of the table is very accurately maintained and it was found in actual practice that the table stops at the end of each cycle of reciprocationto within .0005 of an inch of any prior position.

To accomplish this desirable result, novel and improved means, which are substantially free of backlash, are provided in the machine of the present invention. A double lead feed screw which may be continuously driven at variable speeds is employed in the machine. Operative engagement between the feed screw and the table is accomplished by means of suitable brakes anchored to the table to alternately clamp a respective lead nut rotatably mounted on the feed screw. Backlash is eliminated from the mechanism by mounting the nuts with thrust bearings therebetween so as to prevent any axial movement of the nuts relative to each other or the table when the nut is secured thereto and through the operation of the nuts to always have the working face of each of the threads maintained in Contact with the mating faces of the threads of the lead screw.

It is also desirable in a machine of this type to provide for manually shifting the table and for such purpose the operative engagement between the table and feed screw may be discontinued. At such time, the table may be shifted -by a convenient manually operable handwheel adapted to actuate suitable gearing for shifting such table.

Another desirable feature consists in employing a work head having a swivel center substantially adjacent to the means for mounting a piece of work. This permits the grinding of relatively llarge angled tapers.

Accordingly, it is the general object of the present .invention to provide a grinding machine of novel and improved design and mode of operation in accordance with the foregoing.

Another object of the present invention is to provide a grinding machine of the type mentioned employing a continuously driven double lead feed screw.

A further object of the present invention is to provide a grinding machine, employing a reciprocable table, in which backlash in the table operating mechanism for effecting its reciprocation is entirely eliminated.

A still further object of the present invention is to provide a grinding machine which has means for mounting a piece of work in such manner that relatively large angled tapers may be easily ground;

Other objects and features of novelty of the present invention will either be specifically pointed out or will become apparent when referring, for a better understanding of the present invention, to the following description taken in conjunction with the accompanying drawings, where- 1n:

Figure l is a perspective view looking toward the front of a grinding machine embodying the improvements of the present invention and having cover plates removed to show the driving motor interiorly of the base;

Fig. 2 is a perspective View looking toward the rear of the machine illustrated in Figure 1, with the cover plate removed therefrom to illustrate apparatus interiorly of the base;

Fig. 3 is a front elevational view of the grinding machine of the present invention;

Fig. 4 is an enlarged sectional view of the structure illustrated in Figure 3, taken on the line 4-4 thereof;

Fig. 5 is a sectional view of the structure illustrated in Figure 4, taken on the line 5-5 thereof;

Fig. 6 is an enlarged plan view of the work Vhead with the driving motor illustrated in Fig. 3

omitted, and as viewed from line 6 6 thereof; and

Fig. 7 is an enlarged sectional view of the structure illustrated in Figure 3, taken on the line 1-1 thereof.

Referring to the gures for a more complete description of the grinding machine of the present invention, and particularly to Figures 1, 2 and 3, the machine is shown as being provided with a base generally indicated at l0. This base I0 may be a casting or fabricated from plates of such proportions and of sufficient strength to rigidly support certain of the apparatus of the grinding machine exteriorly thereof and also to 3 provide for supporting a motor interiorly thereof as well as housing other mechanism. Openings therein, which maybe covered in any suitable manner, are provided to gain access to the interiorly housed apparatus.

To provide for the reciprocation of a work head I2, which is to be later more fully described, such work head is mounted upon a table I4. This table I4 is in turn slidably mounted on the base I8, and to provide for such slidable movement of this table, a member I6 having a machined upper surface I8 and a saddle member 26 are mounted in the upper portion of the base I0. These members extend the length of the base and the table I4 is slidably supported by the same with the tongue 22 of the table I4 disposed within the V of the saddle 26.

This reciprocation of table I4 is accomplished by means of the doubleglead feed screw 24 journaledlfor rotation` in a bearing 2 6 provided on the base I andin the, brackets 28 and v38 depending from a bracket plate 32 which is anchored to the lower surface of table I4. A bushing 34 carried by bracket 28 and ya threaded bushing 36 carried by bracket 38 rotatably supports the feed screw ina respectivebracket and, as will hereinafter become more clear, the threaded bushing 36 provides for adjustment to prevent backlash in the mechanism.

As previously stated, this feed screw has a double lead, that its to say,L double threads are provided on,.the same, one being a left-hand thread and the other being a right-hand thread.

A pair ofl leadv nuts 38 and 46 which are threaded oppositely;that is tc say, one has a lefthand thread and V`the other has a right-hand thread,v are mounted in spaced relation on such feed Yscrew to mate with a respective thread thereof. A ballthrust |bearing assembly is positioned` on the feed screw 24 between the lead nuts as indicated at 42.*, :A similar ballbearing assembly 44 is positioned between the bracket 28 and the lead nut l4i) and abearing assembly, indicated at 46, is positioned between the bracket 36 and the .leadnut 38. It will be observed that the bearing assembly 42 enters linto abutting relationship withV the lead nuts 38 .and 46 `and the bearing assemblies 44 andY 46 enter into abutting relationship with a respective lead nut and a respective bracket. The threadedbushing 36 is adjusted to take up any axialplay between the nuts so that they cannot shift axially relative to each other.

When the table Ais driven :in one direction through the securement of the lead nut 38 in iixed relation thereto, the driving face of the lead nut thread is in engagement with the driving face of its mating threadon the lead screw. Since the lead nut 4 6 lis disconnected from thetable, the driving face of its thread will be maintained in driving relation lwith its mating thread of the lead screw while being free to rotate with the screw. When the lead nut 38 is released and the lead nut l40 is secured to thetable, the working faces of the mating threads of the nut 40 and lead screw being in engagement with each other, will drive the table'without any loss of motion between the threads or overrunwof the table. Therefore no backlash can occur upon the'reversal of table movement. Thelead nut 38,'when released, had the. Workingl face of its thread in contact with the workingwface of the thread of the lead screw so that no lost motion occurred between the lead nut 38 andthe lead screw when being driven by the lead screw 40. When thelead screw 40 is again released and the'lead screw 38 secured to the table, the drive between the lead nut 38 and the lead screw will occur without any lost motion as the working faces of the thread of the lead nuts and lead screw are maintained at all times in engagement with each other. No lost motion can occur when changing the direction of movement of the table both because of the engagement of the working faces of the threads of the lead nuts with those of the lead screw and because of the lack of any axial movement of the lead nuts relative to each other or their support. Even though some play may occur axially between the lead nuts, the fact that the working faces of the threads are always maintained in engagement vwould prevent any backlash occurring although some over-travel of the nuts relative to the movementofthe table might occur due to play in the nut securing means. This, however, is prevented through the adjustment of the threaded bushing (i6 which produces a drive through the thrust bearings andthe supportingbrackets -28 and 3U. As pointed out hereinabove, the travel of the: table is maintained within .0005 of an inch.

To effect-driving engagement between the table I4 and feed screw 24, Vmeans are provided -to enter alternately into clamping relationship with lead nuts 38 and 4D. As'mayvbe'seen inFigures 4 and, a brake vgenerally indicated at 48 and another brake generally indicated at 56 are provided adjacentrto each lead nut in positionto 'close upon Asuch nut to retain it against rotation and effect a driving engagement with the feed screw 24. Inasmuch as each brakeis videnticahonly one is herein described. Thus, it may beseen in Figure 4, that brake 50 is provided with a pair of diametrically opposed curved arms 52 and v54 pinned at 88 and 58 to a plate 66 lanchored-to the lower surface of the-bracket plate 32. The-'arms 52 --and- 54 are curved in such .manner as to -t a diametrically opposite portion on the circumferenceof rtheleadnut 4Ii-and it will -be appreciated thatas these arms-areclosed upon thev leadv nut, the nut is held against rotation and the nut and the-table I4 Lwill be driven bythe lead screw in one direction.

The closing vof the arms 52 and-.54 uponra respective lead nutis brought about as follows; `A T-pin 62-is slidablyxmountedv in a crosshead 63 whichV is pivotedlat`64 between the` endsof lthe arm v52. .Between .the head -of the T-pin `82-and theiouter faceof thexzrosshead .63,.a compression spring .66 is mounted on V.the pin. vA nut 65cm thepin is capableof .abutting the innerfaceof the crosshead-to render the spring. inoperative.

`lvhenthearms -52 and.54 .are in the positionY indicated in Figure 4, the. springV .66 .exerts a force tendingto close the arms .52 and 54 upongthe lead nut 4.6, as will hereinafter becomemore `clear. To bring the T-pin 62 into Opelitvcposition,

which .is adaptedto .berbmusht into, alignment withl a lever 'I6 to which the free .end of the T-pin 62 is fixed in `extension thereof. The lever .'IIJ is pinned at 'I2 to arm 54 and at I4 to the lever 68.

Thelever is pivoted Vto a piston. 'I6 which is acto permit the nut 65 to strike the crosshead 63, the position indicated by the dashed lines in Figure 4. When this occurs, the curved arms 52 and 54 are separated and the brake no longer secures the lead nut 49 which is free to rotate with the lead screw and movement of table I4 in one direction is terminated.

Upon the actuation of the solenoid 'I8, the piston v'I6 moves inwardly, causing the lever I9 to move to the position illustrated in Figure 4. This shifts the lever 68 and T-pin 62 to the right moving the nut 65 away from the crosshead 63 and permitting the spring 66 to move the arms 52 and 54 toward each other to apply the brake to the lead nut 49 for preventing its rotation and thereby driving table I4 in one direction.

This solenoid brake herein described is manufactured by the Cutler-Hammer Manufacturing Company of Milwaukee, Wisconsin, and has been slightly altered to adapt the same for use in the grinding machine of the present invention, and is not further described herein as it or any well known solenoid actuated brake can be employed for engaging and securing the head against rotation.

The action of the brake 48 on the lead nut 38 is identical to that explained in connection with brake 59 and it will now be appreciated, inasmuch as the thread of lead nut 38 is opposite to the thread of lead nut 49, that upon alternately engaging the brakes 48 and 59 with their respective lead nuts, it is possible to effect reciprocation of the table I4.

The driving of the feed screw 24, to effect this reciprocation of the table I4, may be accomplish ed by means of a prime mover in the form of an electric motor 94. The motor drives through a speed reducer 85 and pulley 86 to drive a belt 88 and a pulley 99 integrally connected to the feed screw 24. Thus, it is possible by varying either the speed of the motor 84 or adjusting the vspeed reducer 85, to drive the feed screw 24 at variable speeds for effecting the reciprocation of the table I4 at any desirable speed.

To produce the automatic reciprocation of the table I4, dogs 92 and 94 are adjustably mounted ina T-slot 96 provided in the forward side of the table I4. The dogs 92 and 94, respectively, may be slidably adjusted in the T-slot 96 to provide the desired stroke for the table I4 and in this adjusted position are adapted to Contact respectively switches 98 and |99. The switches effect the actuation of the solenoid 'I8 for the brake 59 and solenoid (not shown) for the brake 48 for causing such brakes to alternately engage a respective lead nut to effect travel of the table I4 first, in one direction, and then in the other. The electric circuits by which this actuation is accomplished are not described inasmuch as they may be any suitable circuit designed to accomplish this actuation in timed relation to the travel of the table I4.

When it is desired for purposes of set up or other reason to effect movement of the table I4 manually, the electrical connection to the switches 9B and |99 may be opened to prevent the actuation of the brakes 48 and 59. This frees lead nuts 38 and 49, so that they are free to rotate when the table is driven manually.

After the lead nuts are thus rendered ineffective, the table I4 may be shifted manually by means of the following mechanism. A rack |92, which may be seen in Figure 7, is anchored to depend from the lower surface of the table I4 and adapted to mesh a pinion |94. The pinion |94 is formed on the inner end of the shaft |96 which is journaled for rotation within the bearing housing |98, on the base I9, and in the bear' ing provided in a gear housing ||9 attached to= the outer face of the front Wall of the base I9.- At the other end of the shaft |96, a gear ||2 isy fixed to mesh with a pinion I4 which is mounted on a shaft I I 5 journaled for rotation in the gear' housing ||9 opposite to the shaft |96. The rota# tion of the pinion I I4 may be accomplished by a conveniently accessible hand wheel ||6 also attached to the shaft 5, and it will be seen that the rotation of this gear will effect a similar rotation of the gear I I2 and the pinion |94, serving to shift the table I4 by means of the rack |92.

To provide for mounting a workpiece on thegrinding machine of this invention, the pre-- viously mentioned workhead I2 which, as stated in the foregoing, is mounted on the table I4 pro-- vides a Workholder IIS. A workpiece may be secured in any suitable manner to the workholderv IIB to be rotatably driven by means of a motorl The motor' drives the spindle |22 to which the WorkholderI ||8 may be fixed and such motor is independentof the main drive motor 84. The motor |29 is.

|29 mounted on the workhead I2.

controlled by means of a separate electrical cir` cuit', and consequently, it is not necessary that the work be driven continuously but only during.

the grinding operation.

This workhead I2is mounted for movement infected by means of a feed screw |28 which issy rotatably supported in the base |26 and adapted to threadably engage a lead nut I 39 carried by the slide |24. At one end of the feed screw I 28,. a nut |32 is fixed to which an operating handle: may be attached for rotating the feed screw and? also to serve as a stop for lead nut |39, prevent-- ing movement of slide |24 except in a direction away from the nut I 32. It will be observed, therefore, that as the feed screw |28 is turned, the slide |25 will be shifted to move the Workhead I2 in one direction, transversely of the table I4.

The workhead I2 may be also moved arcuately about a center |34 which serves as a pivot, as illustrated in Fig. 6. For this purpose, the Workhead I2 is mounted upon a sector-shaped upper slide |36 adapted to be slidably moved arcuately about the center |34 on the cross slide |24. A pair of clamps I 31 and |38 are mounted on the cross slide |24 to secure the upper slide I 3B in adjusted position and may be released to permit the arcuate movement of upper slide.

The center |34 is integral with the upper slide 36 and extends through an opening provided therefor in the cross slide |24 where it is secured by a bolt I 49. It will be noted that this center |34 is located adjacent to the workholder IIB. This brings the point about which the work is pivoted for grinding a taper close to the work, making it possible to grind large angled tapers.

To mount a grinding head, generally indicated at |42, on the machine of the present invention, a bridge |44 is formed integral with the base I9 at one end of the base. The bridge |44 extends in a direction transversely of the table I4 and in overlying relation thereto so as to not interfere with its reciprocation. As the table I4 reciprocates, the workhead may bring a piece of Work into engagement with a grinding Wheel |46 driven by a motor |48"'on the grinding head. Similar to the motor |2||"n the w'rkh'ead I2, the motor |4815 independent f the main drive'm-l tor 84T and is controlled by a separate electric circuit.

As in theA case of the rworkhead |2,` the grinding head is shiftable 'in one direction'transversly of table Ill.` For this shifting', the'rei's 'formed' integrally with the grinding head |42, a cross slide |50. The slide |50 is adapted to lbe s'hift'ed"lat erally of the table lll, but opposite vto `thedirec tion in which -the'cross slide- |24 of the Work'- head may be shifted. The 'cross' slide v| 5D is slidably positionedon a dovetail-portion of the bridge |48 to be shifted by a feed screw |52. The feed screw |52'is rotatably journaled in 'thedovetai'l portion and adapted to threadably receive a lead nutV (not shown) lCarried -by cross slide |59. In order to effect rotation of feed screw |52,L a hand wheel |54 is positioned conveniently at the 'outer end thereof.

Thus, with the workhead V|2 -shiftable laterally on the table Ill in one direction and, with grindinghead |42 shiftable laterally on table i4 vin an opposite direction, it is possible to accommodate on -thegrindingmachine of the present invention a workpiece of considerable size.

Freni the foregoing, it will be appreciated that the grinding machine of the present invention is of novel and improved designand particularly provides novel and improved means for effecting reciprocation of a workpiece as the same is ground.

What is claimed is:r`

1. In a machine, a base, a table slidably mounted for reciprocation on said base, meansmounting spacedebrackets -to depend from the bottom of said table, a double lead feedscrew rotatably supported by -said base and said brackets, separate lead nuts havingv opposite -hand threads mounted qin spaced relation on said-feed screw and within 'said brackets, a separate thrust bearing betweenthelead nuts and between each lead nut'an'd a 'respectiveY bracket, a bushing in one bracket in surrounding'reIationshipto said feed screw, and'a pressure applying means carried `by thebther'bracket tolact on the adjacent thrust bearing for eliminating any axial movement between the nuts and table.

2. rIrna maehinar'abase, a table slidably mounted'for'recip-rocation on said base, means mounting-spaced brackets' to depend from theV bottom of sai'dtafalef'a double lead feed screw rotatably supported bysaid'bas and said brackets, separated lead Anuts having opposite hand threads mcuntedin spa'cedrelation on said feed screw and within said brackets, a separate thrust bearing between the leadnuts and between reach lead nut 'anda' respective bracketa bushing in one bracket' in'surrounding relationship to `said feed screw; and a rotatable bushing threadably re-V tained by the other bracket adapted to be turned inwardly to Vbear upon the adjacent thrust bearing for eliminating'any axial movement between the bearings, lead nuts and brackets.

JOHN M. CHRISTMAN.

REFERENCES crrEn The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 463,917 Wheeler Nov. 10, 1891 856,978 Mowat June 11, 1907 1,186,616 Strecker June 13, 1916 1,392,172 Keller Sept. 27, 1921 1,558,721 Thompson Oct. 27, 1925 1,896,752 Raule Feb. 7, 1933 2,389,224 Wessman Nov. 20, 1945 

